CN114868313A

CN114868313A - Packed bed filter for trapping metal fluoride dust in laser discharge cavity

Info

Publication number: CN114868313A
Application number: CN202080089581.4A
Authority: CN
Inventors: U·尼曼; W·D·吉莱斯皮
Original assignee: Cymer LLC
Current assignee: Cymer LLC
Priority date: 2019-12-23
Filing date: 2020-12-10
Publication date: 2022-08-05
Also published as: KR20220100989A; WO2021133568A1; JP7394224B2; US20230008480A1; JP2023507274A; TW202139547A; TWI760019B

Abstract

A light source arrangement (200) comprises a gas discharge stage (210) and a metal fluoride trap (300). The gas discharge stage comprises an optical amplifier (206) and a set of optical elements (250, 260). The optical amplifier includes a chamber (211) configured to hold a gas discharge medium (213) that outputs a light beam. The set of optical elements is configured to form an optical resonator around the optical amplifier. The metal fluoride trap is configured to trap metal fluoride dust generated from the gas discharge stage. The metal fluoride trap includes an electrostatic precipitator (320) and a packed bed filter (400, 402, 404) disposed about the electrostatic precipitator. The packed bed filter includes a plurality of beads (406, 408) configured to absorb the metal fluoride dust (208).

Description

Packed bed filter for trapping metal fluoride dust in laser discharge cavity

Cross Reference to Related Applications

The present application claims priority from U.S. application No. 62/953,101 entitled packet-BED FILTER FOR METAL FLUORIDE DUST TRAPPING IN LASER DISCHARGE CHAMBERS filed on 23/12/2019, which is incorporated herein by reference in its entirety.

Technical Field

The present disclosure relates to light source apparatus and systems, such as light sources having metal fluoride traps for use in lithographic apparatus and systems.

Background

A lithographic apparatus is a machine that is configured to apply a desired pattern onto a substrate. Lithographic apparatus can be used, for example, in the manufacture of Integrated Circuits (ICs). A lithographic apparatus may, for example, project a pattern of a patterning device (e.g., mask, reticle) onto a layer of radiation-sensitive material (resist) provided on a substrate.

To project a pattern on a substrate, a lithographic apparatus can use electromagnetic radiation. The wavelength of this radiation determines the minimum size of features that can be formed on the substrate. Lithographic apparatus using Extreme Ultraviolet (EUV) radiation having a wavelength in the range 4nm to 20nm, for example 6.7nm or 13.5nm, may be used to form smaller features on a substrate than lithographic apparatus using Deep Ultraviolet (DUV) radiation having a wavelength of, for example, 157nm or 193nm or 248 nm.

A Master Oscillator Power Amplifier (MOPA) is a two-stage optical resonator arrangement that produces a highly coherent amplified light beam. The performance of a MOPA may critically depend on the Master Oscillator (MO). The electrodes of the MO surrounding the gas discharge medium may deteriorate over time and generate metal fluoride dust. Metal fluoride dust can deposit on the optical window of the MO and cause optical damage. In addition, the circulation of metal fluoride dust in MO also causes a decrease in discharge voltage from the electrode, and a decrease in laser performance.

Disclosure of Invention

Accordingly, there is a need to improve metal fluoride dust trapping capabilities, reduce metal fluoride dust in gas discharge media and on optical windows, improve flow distribution control through metal fluoride traps, provide effective cleaning and/or replacement of metal fluoride trap components, and extend the lifetime of the master oscillator.

In some embodiments, a light source apparatus includes a gas discharge stage and a metal fluoride trap. The gas discharge stage comprises an optical amplifier and a set of optical elements. The optical amplifier includes a chamber configured to hold a gas discharge medium that outputs a light beam. The set of optical elements is configured to form an optical resonator around the optical amplifier. The metal fluoride trap is configured to trap metal fluoride dust generated from the gas discharge stage. The metal fluoride trap includes an electrostatic precipitator and a packed bed filter disposed about the electrostatic precipitator. The packed bed filter includes a plurality of beads configured to absorb the metal fluoride dust. The absorption may include mechanically trapping the dust particles in interstitial spaces between the beads, and/or chemically interacting (e.g., adsorbing) with the surface of the beads.

In some embodiments, the packed bed filter comprises a total surface area configured to control the flow of the gas discharge medium through the metal fluoride trap.

In some embodiments, the packed bed filter comprises a plurality of packed bed filters separated by baffles. In some embodiments, the plurality of packed bed filters are different. In some embodiments, the plurality of packed bed filters vary in surface area. In some embodiments, the plurality of packed bed filters have different packing densities.

In some embodiments, the plurality of beads are spherical and have a smooth polished outer surface. In some embodiments, the plurality of beads comprises a fluoride corrosion resistant material. In some embodiments, the plurality of beads comprises a plurality of first beads, and a plurality of second beads different from the plurality of first beads.

In some embodiments, the gas discharge medium comprises an excimer medium and/or an exciplex medium (which may also be referred to as an excimer medium). In some embodiments, the gas discharge medium comprises F ₂ ArF, KrF and/or XeF.

In some embodiments, the set of optical elements includes an Optical Coupler (OC) in optical communication with a first optical port of the chamber, and a line width narrowing module (LNM) in optical communication with a second optical port of the chamber.

In some embodiments, the light source apparatus further comprises a pressure control system coupled to the gas discharge stage and configured to direct a portion of the gas discharge medium to flow through the input port of the metal fluoride trap, through the packed bed filter, and through the one or more output ports of the metal fluoride trap.

In some embodiments, a metal fluoride trap configured to trap metal fluoride dust generated in a gas discharge medium of a gas discharge stage includes an electrostatic precipitator and a packed bed filter disposed about the electrostatic precipitator. The packed bed filter includes a plurality of beads configured to absorb metal fluoride dust in the gas discharge medium.

In some embodiments, the plurality of beads are all spherical. In some embodiments, each bead is about 1mm to about 10mm in diameter. In some embodiments, each bead comprises a smooth polished outer surface.

In some embodiments, the plurality of beads comprises a fluoride corrosion resistant material. In some embodiments, the fluoride corrosion resistant material comprises a glass-like component, a crystalline component, a metal, and/or an oxide. In some embodiments, the fluoride corrosion resistant material comprises aluminum, duralumin, alumina, nickel, monel, brass, copper, zinc, calcium boride, and/or calcium fluoride.

In some embodiments, the plurality of beads comprises a plurality of first beads, and a plurality of second beads different from the plurality of first beads. In some embodiments, the plurality of first beads has a first size and the plurality of second beads has a second size different from the first size. In some embodiments, the plurality of first beads comprises a first material and the plurality of second beads comprises a second material different from the first material.

In some embodiments, a method of trapping metal fluoride dust generated in a gas discharge medium of a gas discharge stage in a metal fluoride trap includes assembling a dust extraction tube assembly including a plurality of dust extraction tubes located between a first tube end support and a second tube end support. In some embodiments, the method further comprises assembling a plurality of packed bed filters in a dust extraction tube assembly around the electrostatic precipitator to form a packed bed filter assembly. Each packed bed filter includes a plurality of beads configured to absorb metal fluoride dust in the gas discharge medium. In some embodiments, the method further comprises inserting the packed bed filter assembly into a metal fluoride trap. In some embodiments, the method further comprises directing a gas discharge medium to flow through the metal fluoride trap. In some embodiments, the method further comprises trapping the metal fluoride dust in a packed bed filter assembly.

In some embodiments, assembling the plurality of packed bed filters comprises packing the plurality of beads between the plurality of dust removal tubes. In some embodiments, the filling includes filling a plurality of inner beads in a plurality of inner dust extraction tubes, and filling an outer plurality of outer beads different from the plurality of inner beads in a plurality of outer dust extraction tubes. In some embodiments, the plurality of outer beads have a different surface area and/or packing density than the plurality of inner beads.

In some embodiments, the method further comprises: the method further includes removing the plurality of beads from the packed bed filter assembly, washing the plurality of beads, and reassembling the plurality of beads in the packed bed filter assembly. In some embodiments, the method further comprises removing the plurality of beads from the packed bed filter assembly and reassembling the plurality of second beads in the packed bed filter assembly.

Embodiments of any of the techniques described above may include EUV light sources, DUV light sources, systems, methods, processes, apparatuses, and/or devices. The details of one or more implementations are set forth in the accompanying drawings and the description below. Other features will be apparent from the description and drawings, and from the claims.

Further features and exemplary aspects of the embodiments, as well as the structure and operation of the embodiments, are described in detail below with reference to the accompanying drawings. It should be noted that the embodiments are not limited to the specific embodiments described herein. These examples are presented herein for illustrative purposes only. Other embodiments will be apparent to persons skilled in the relevant art(s) based on the teachings contained herein.

Drawings

The accompanying drawings, which are incorporated herein and form a part of the specification, illustrate embodiments and, together with the description, further serve to explain the principles of the embodiments and to enable a person skilled in the pertinent art(s) to make and use the embodiments.

FIG. 1 is a schematic view of a lithographic apparatus according to one embodiment.

Fig. 2 is a schematic view of a light source device according to an embodiment.

Fig. 3 is a schematic cross-sectional view of a metal fluoride well of the light source apparatus shown in fig. 2 according to one embodiment.

Fig. 4 is a schematic cross-sectional view of a packed bed filter assembly of the metal fluoride trap shown in fig. 3 according to an embodiment.

Figure 5 illustrates a flow diagram for trapping metal fluoride dust according to one embodiment.

Features and exemplary aspects of the embodiments will become more apparent from the detailed description set forth below when taken in conjunction with the drawings, in which like reference characters identify corresponding elements throughout. In the drawings, like reference numbers generally indicate identical, functionally similar, and/or structurally similar elements. Further, in general, in the figures, the left-most digit(s) of a reference number identifies the figure in which the reference number first appears. The drawings provided in this disclosure should not be construed as being drawn to scale unless otherwise indicated.

Detailed Description

This specification discloses one or more embodiments that incorporate the features of this invention. The disclosed embodiment(s) is (are) merely an example of the invention. The scope of the invention is not limited to the disclosed embodiment(s). The invention is defined by the appended claims.

Reference in the specification to "one embodiment," "an example embodiment," etc., described or illustrated in the embodiment(s) indicates that the embodiment(s) described may include a particular feature, structure, or characteristic, but every embodiment may not necessarily include the particular feature, structure, or characteristic. Moreover, such phrases are not necessarily referring to the same embodiment. Further, when a particular feature, structure, or characteristic is described in connection with an embodiment, it is submitted that it is within the knowledge of one skilled in the art to effect such feature, structure, or characteristic in connection with other embodiments whether or not explicitly described.

Spatially relative terms, such as "lower," "below," "lower," "upper," "above," "upper," and the like, may be used herein to facilitate describing the relationship of one element or feature to another element(s) or feature(s) as illustrated in the figures. Spatially relative terms will encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. The device may be in other orientations (rotated 90 degrees or other orientations) and the spatially relative descriptors used herein interpreted accordingly.

The terms "about" or "substantially" or "approximately" as used herein indicate a given amount of value that may vary based on the particular technique. The terms "about" or "substantially" or "approximately" may indicate a given amount of a value (e.g., ± 1%, ± 2%, ± 5%, ± 10% or ± 15% of the value) that varies, for example, within 1% to 15% of the value, based on the particular technique.

As used herein, the term "absorb" or "adsorb" may include both absorb and adsorb.

Embodiments of the disclosure may be implemented in hardware, firmware, software, or any combination thereof. Embodiments of the disclosure may also be implemented as instructions stored on a machine-readable medium, which may be read and executed by one or more processors. A machine-readable medium may include any mechanism for storing or transmitting information in a form readable by a machine (e.g., a computing device). For example, a machine-readable medium may include Read Only Memory (ROM); random Access Memory (RAM); a magnetic disk storage medium; an optical storage medium; a flash memory device; electrical, optical, acoustical or other form of propagated signals (e.g., carrier waves, infrared signals, digital signals, etc.), and others. Further, firmware, software, routines, and/or instructions may be described herein as performing certain actions. However, it should be understood that such descriptions are merely for convenience and that such actions in fact result from computing devices, processors, controllers, or other devices executing the firmware, software, routines, instructions, etc.

However, before describing such embodiments in more detail, it is beneficial to present an example environment in which embodiments of the present disclosure can be implemented.

Exemplary lithography System

FIG. 1 shows a lithographic system comprising a radiation source SO and a lithographic apparatus LA. The radiation source SO is configured to generate an EUV and/or DUV radiation beam B and to provide the EUV and/or DUV radiation beam B to the lithographic apparatus LA. The lithographic apparatus LA comprises an illumination system IL, a support structure MT configured to support a patterning device MA (e.g. a mask), a projection system PS, and a substrate table WT configured to support a substrate W.

The illumination system IL is configured to condition the EUV and/or DUV radiation beam B before it is incident on the patterning device MA. Hence, the illumination system IL may comprise a facet field lens device 10 and a facet pupil lens device 11. The faceted field lens arrangement 10 and the faceted pupil lens arrangement 11 together provide a beam B of EUV and/or DUV radiation having a desired cross-sectional shape and a desired intensity distribution. The illumination system IL may comprise other mirrors or devices in addition to or instead of the facet field lens device 10 and the facet pupil lens device 11.

After such conditioning, the EUV and/or DUV radiation beam B interacts with the patterning device MA. This interaction may be reflective (as shown), which may be preferred for EUV radiation. This interaction may be transmissive, which may be preferred for DUV radiation. As a result of this interaction, a patterned beam B' of EUV and/or DUV radiation is generated. The projection system PS is configured to project a patterned beam B' of EUV and/or DUV radiation onto a substrate W. To this end, the projection system PS may comprise a plurality of

mirrors

13, 14 configured to project the patterned EUV and/or DUV radiation beam B' onto a substrate W held by the substrate table WT. The projection system PS may apply a reduction factor to the patterned EUV and/or DUV radiation beam B' to form an image having smaller features than corresponding features on the patterning device MA. For example, a reduction factor of 4 or 8 may be applied. Although the projection system PS is shown in fig. 1 as having only two

mirrors

13, 14, the projection system PS may also comprise a different number of mirrors (e.g. 6 or 8 mirrors).

The substrate W may include a previously formed pattern. In this case, the lithographic apparatus LA aligns an image formed by the patterned EUV and/or DUV radiation beam B' with a pattern previously formed on the substrate W.

Exemplary light Source device

As described above, the Master Oscillator Power Amplifier (MOPA) is a two-stage optical resonator arrangement. A Master Oscillator (MO), such as the first optical resonator stage, produces a highly coherent optical beam. A Power Amplifier (PA), such as a second optical resonator stage, increases the optical power of the optical beam while maintaining beam characteristics. The MO may include a gas discharge chamber, an Optical Coupler (OC), and a line width narrowing module (LNM). The OC and LNM can surround a gas discharge chamber to form an optical resonator.

The performance of a MOPA may be strictly dependent on the MO, e.g. the optical window of the MO of the output beam. Excimer lasers utilize an excimer medium to output Extreme Ultraviolet (EUV) radiation andand/or Deep Ultraviolet (DUV) radiation. Other gas lasers may use other media (e.g., F) ₂ A laser). The excimer is composed of the same species (e.g. Ar) ₂ 、Kr ₂ 、Xe ₂ ) Two atoms forming a short-lived molecule ("excimers"). The term "excimer" also refers to an exciplex medium ("exciplex") in which short-lived molecules are formed from two or more species (e.g., ArF, KrCl, KrF, XeBr, XeCl, XeF). Surrounding a gas discharge medium (e.g. F) ₂ ArF, KrF, and/or XeF) may degrade over time and generate metal fluoride dust (e.g., having an average diameter of about 2.0 μm). Metal fluoride dust can deposit on the optical window of the MO and cause optical damage (e.g., localized thermal adsorption and/or heating). In addition, the circulation of the metal fluoride dust in the MO also causes a reduction in discharge voltage from the electrode and a decrease in laser performance.

In some embodiments, a Metal Fluoride Trap (MFT) may be coupled to the chamber of the MO to reduce contamination of the gas discharge medium. For example, certain MFTs have been previously described in U.S. patent No. 6,240,117, published 5-29-2001 and U.S. patent No. 7,819,945, published 10-26-2010, which are hereby incorporated by reference in their entirety. As a portion of the gas discharge medium passes through the MFT, metal fluoride dust in the contaminated gas discharge medium is absorbed in the trap filter, and any remaining particles are collected by the electrostatic precipitator. The electrostatic precipitator induces electrostatic charges in the dust particles flowing through the MFT via a strong electric field (e.g., applying a potential of several kV). For example, a voltage may be applied to a center wire that passes axially through the dust removal tube (e.g., cylindrical), creating an electrostatic charge on the inner surface of the dust removal tube. Any remaining metal fluoride dust adheres to the inner surface of the dust removal tube. The resulting cleaning gas may be circulated back into the MO chamber through the optical window housing to prevent dust from entering the window.

In some embodiments, the MFT mechanism uses a multi-layer mesh screen (e.g., a brass woven mesh) with an electrostatic precipitator. However, mesh screens may not be easily cleaned after use and may need to be replaced over time. Furthermore, the mesh screen may collect metal fluoride dust (e.g., hot spots in high density areas) that affects the flow through the MFT disproportionately over time. Over time, dust trapping capability (e.g., total surface area) can decrease, which is a key limiting factor in laser lifetime and beam output to, for example, a DUV lithographic apparatus.

In some embodiments, a packed bed filter may be used for the filtration media, such as gas discharge media. In general, packed bed filters have been used in chemical processing (e.g., chemical reactors, distillation, scrubbers, etc.) and environmental engineering (e.g., air filtration, water filtration, waste filtration, etc.). Generally, in chemical applications, packed beds are used to provide maximum surface area for the chemical conversion of fluids by thermal or catalytic processes and then release the fluid back into the stream without any residue on the packing material. The packed bed filter may include structured packing (e.g., raschig rings, columns, etc.) and/or catalyst particles or absorbents (e.g., zeolite pellets, activated carbon, sand, gravel, etc.). For example, when an absorbent (e.g., spheres) is randomly added to a container and then shaken, a so-called "irregular" or "plugged" packing configuration is typically formed, which is the highest packing density without careful consideration of assembly. The density of such irregular packing is typically about 64%. The packed bed filter used in the excimer system may be different from a general packed bed filter. For example, a packed bed filter in an excimer system should be corrosion resistant (e.g., F) ₂ 、Cl ₂ Etc.) and should not be contaminated with gas discharge medium.

In some embodiments, an MFT having a packed bed filter comprising a plurality of beads (e.g., brass, alumina, crystals, glass-like, etc.) may (1) enhance metal fluoride dust trapping capabilities (e.g., greater surface area than previous traps such as brass woven mesh); (2) provide control over flow distribution (e.g., uniform and/or optimized flow) in the MFT due to bead type and/or bead distribution; (3) customizing and/or optimizing flow, capture capacity, and/or flow distribution in the MFT by using customized beads and/or different arrangements of beads (e.g., size, shape, material, roughness, surface area, packing density, functionalization, etc.); and (4) after sufficient adsorption of the metal fluoride dust, allows for effective cleaning and/or replacement of the packed bed filter.

In some embodiments, a packed bed filter comprising a plurality of beads can have an irregular packing configuration (e.g., about 64% packing density). For example, the resulting porosity may be used with the internal volume of the MFT and the incoming flow to calculate the flow rate of the chamber gas through the MFT. In some embodiments, space-occupying bodies (e.g., smaller beads or sub-beads) may be added for regulating the flow rate of the chamber gas through the MFT.

In some embodiments, the packed bed filter comprising a plurality of beads may be arranged as random loose-fill (RLP), random close-fill (RCP) (e.g., "irregular" packing configurations), single-size spherical packing (e.g., face-centered-cubic (FCC)), multi-size spherical packing (e.g., FCC with smaller diameter beads to fill voids), and the like. For example, a plurality of beads may be arranged as RLP (e.g., packing density of about 60%), RCP (e.g., packing density of about 64%), single-size spherical packing (e.g., packing density of about 74%), and/or multi-size spherical packing (e.g., packing density of about 93%)

In some embodiments, the bead diameter of a packed bed filter comprising a plurality of beads (e.g., spheres) may enable optimization of particle capture capacity and the probability of blocking the chamber gas flow. For example, the bead diameter and preferred volume of captured dust particles can be determined such that the likelihood of clogging (e.g., choked flow) and/or complete clogging is minimized (e.g., models and/or calculations can be minimized based on the fact that the flow is largely slowed primarily near the bead's contact points, where nearly stagnant flow conditions allow particles to separate from the flow and adhere first to the bead surface, then with dust particle agglomeration).

In some embodiments, the function of a packed bed filter comprising a plurality of beads (e.g., spheres) is in contrast to the general packed bed filters described above for chemical applications, such that the beads of the packed bed filter in the MFT provide a surface to absorb and/or capture dust particles (e.g., rather than subsequently releasing the dust particles back into the flow without any residue on the packing material).

In some embodiments, the effect of a packed bed filter containing a plurality of beads (e.g., spheres) is to improve mixing by achieving random and/or varying flow paths that favor screens (e.g., woven brass mesh) that will saturate on preferred surfaces and result in surface by-pass flow with reduced capture effectiveness. For example, flow can be dynamically balanced through a path of minimum flow resistance without variation in capture effectiveness due to size-controlled packing density of the beads (e.g., irregular packing configurations with packing densities of about 64%).

In some embodiments, a packed bed filter containing a plurality of beads (e.g., spheres) can be pre-assembled as a cylindrical ring filter cartridge that can be slid into the MFT. For example, a cylindrical ring filter element may provide an assembled and packed bed without exposing the entire MFT to further options of vibration and/or manipulation that may affect the function of the MFT.

Embodiments of light source apparatus and systems as discussed below can improve metal fluoride dust trapping capabilities, reduce metal fluoride dust in gas discharge media and on optical windows, improve flow distribution control through metal fluoride traps, provide effective cleaning and/or replacement of metal fluoride trap components, and extend the lifetime of a master oscillator to provide, for example, an excimer laser beam to a DUV lithographic apparatus.

Fig. 2 to 4 illustrate a light source apparatus 200 according to various exemplary embodiments. Fig. 2 is a schematic diagram of a light source apparatus 200 according to an example embodiment. Fig. 3 is a schematic cross-sectional view of a metal fluoride trap 300 of the light source apparatus 200 shown in fig. 2 according to an example embodiment. Fig. 4 is a schematic cross-sectional view of a packed bed filter assembly 400 of the metal fluoride trap 300 shown in fig. 3, according to an example embodiment.

Fig. 2 illustrates a light source apparatus 200 according to various exemplary embodiments. The light source apparatus 200 may be configured to reduce metal fluoride dusting contamination in a gas discharge stage 210 (e.g., MO) and provide a highly coherent and aligned light beam (e.g., light beam 202) to, for example, a DUV lithographic apparatus (e.g., LA). The light source apparatus 200 may also be configured to reduce metal fluoride dust accumulation on the first optical window 218 and the second optical window 220, and to improve the lifetime and laser performance of the gas discharge stage 210 (e.g., MO). Although light source apparatus 200 is illustrated in FIG. 2 as a stand-alone apparatus and/or system, embodiments of the present disclosure may also be used with other optical systems, such as, but not limited to, a radiation source SO, a lithographic apparatus LA, and/or other optical systems. In some embodiments, the light source apparatus 200 can be a radiation source SO in a lithographic apparatus LA. For example, the EUV and/or DUV radiation beam B may be the beam 202. In some embodiments, light source apparatus 200 may be a MOPA (not shown) formed from a gas discharge stage 210 (e.g., MO) and a power loop amplifier (PRA) stage (e.g., PA).

As shown in fig. 2, light source apparatus 200 may include a gas discharge stage 210, a voltage control system 230, a pressure control system 240, and a Metal Fluoride Trap (MFT) 300. In some embodiments, all of the components listed above may be housed in a three-dimensional (3D) frame 201. For example, the 3D frame 201 may include metal (e.g., aluminum, steel, etc.), ceramic, and/or any other suitable rigid material.

The gas discharge stage 210 may be configured to output a highly coherent light beam (e.g., light beam 202). The gas discharge stage 210 may include an optical amplifier 206, an Optical Coupler (OC)250, and a line width narrowing module (LNM) 260. In some embodiments, OC 250 may include a first optical resonator element 252 and LNM 260 may include a second optical resonator element 262. The optical resonator 270 may be defined by the OC 250 (e.g., via the first optical resonator element 252) and the LNM 260 (e.g., via the second optical resonator element 262). First optical resonator element 252 may be partially reflective (e.g., a partially reflective mirror) and second optical resonator element 262 may be reflective (e.g., a mirror, a grating, etc.) to form optical resonator 270. Optical resonator 270 may direct light generated by optical amplifier 206 to pass through and into optical amplifier 206 a fixed number of times to form optical beam 202. In some embodiments, the gas discharge stage 210 may output the light beam 202 to a PRA stage (not shown) that is part of a MOPA arrangement.

As shown in fig. 2, the optical amplifier 206 may include a chamber 211, a first optical window 218, and a second optical window 220. The chamber 211 may be configured to hold a gas discharge medium 213 within the first optical window 218 and the second optical window 220. The chamber 211 may include an electrode 204, metal fluoride dust 208, a blower 212, a gas discharge medium 213, an input port 214 directed to the MFT 300, a first output port 222 directed to the first optical window 218, and a second output port 224 directed to the second optical window 220. The input port 214 may be configured to pass a portion of the gas discharge medium 213 with the metal fluoride dust 208 within the chamber 211 into the MFT 300. The first and

second output ports

222, 224 may be configured to pass portions of the gas discharge medium 213 (e.g., the cleaning gas from which the metal fluoride dust 208 is removed) from the MFT 300 back through the chamber 211 to the first and second

optical windows

218, 220, respectively.

The optical amplifier 206 may be optically coupled to the OC 250 and the LNM 260. The optical amplifier 206 may be configured to output the light beam 202. The beam 202 may be generated in a gas discharge medium 213 between electrodes 204 within a chamber 211, the chamber 211 being located in an optical resonator 270 defined by the OC 250 and the LNM 260. The chamber 211 may be coupled to the MFT 300 and the first and second

optical windows

218 and 220. A gas discharge medium 213 may be circulated between the electrodes 204 within the chamber 211 by a blower 212. In some embodiments, the blower 212 may be a tangential blower. A portion of the gas discharge medium 213 may be extracted at an input port 214 downstream of the blower 212 and directed through the MFT 300. The cleaning gas may be circulated back into the chamber 211 through the first optical window 218 and the second optical window 220 to remain free of laser debris (e.g., metal fluoride dust 208). In some embodiments, the blower 212 and/or the pressure control system 240 (e.g., the vacuum line 244) may maintain a flow rate from the chamber 211 to the MFT 300 (e.g., the input port 214) at about 100 sccm.

The gas discharge medium 213 may be excited, for example by an electrical discharge, to output light that is amplified in the laser cavity to produce a beam 202 (e.g. 157nm or 193nm or 248 nm). In some embodiments, the gas discharge medium 213 may include a gas for excimer laser (e.g., Ar) ₂ 、Kr ₂ 、F ₂ 、Xe ₂ ArF, KrCl, KrF, XeBr, XeCl, XeF, etc.). For example, the gas discharge medium 213 may comprise ArF, and upon excitation (e.g., application of a voltage) by the surrounding electrode 204 in the chamber 211, the output beam 202 (e.g., 157nm or 193nm or 248nm) passes through the first optical window 218 and the second optical window 220. In some embodiments, the gas discharge medium 213 may comprise an excimer medium. For example, the gas discharge medium 213 may include F ₂ ArF, KrF and/or XeF.

The OC 250 may be configured to be in optical communication with the second optical window 220. In some embodiments, OC 250 may be configured to partially reflect the light beam and form part of optical resonator 270. For example, OC has been previously described in U.S. patent No. 7,885,309, published on 8/2/2011, which is incorporated herein by reference in its entirety. As shown in fig. 2, the OC 250 may include a first optical resonator element 252 to direct light (e.g., the beam 202) from the optical amplifier 206 back to the optical amplifier 206 and/or to the output beam 202. The first optical resonator element 252 may be adjusted (e.g., tilted).

LNM 260 can be configured to be in optical communication with first optical window 218. In some embodiments, LNM 260 can be configured to provide spectral lines that are narrowed into optical beams and form part of optical resonator 270. For example, LNM has been previously described in U.S. patent No. 8,126,027, published on day 2/28 2012, which is incorporated herein by reference in its entirety. As shown in fig. 2, LNM 260 can include a second optical resonator element 262 to direct light (e.g., beam 202) from optical amplifier 206 back toward OC 250 to optical amplifier 206. The second optical resonator element 262 may be adjusted (e.g., tilted, angled).

The voltage control system 230 may be configured to apply high voltage electrical pulses across all electrodes 204 within the chamber 211 to excite the gas discharge medium 213 to output the beam 202 (e.g., 157nm or 193nm or 248 nm). Voltage control system 230 may include a voltage source line 232. In some embodiments, voltage control system 230 may include a high voltage source (not shown), a voltage compression amplifier (not shown), a pulse energy monitor (not shown), and/or a controller (not shown) for providing high voltage electrical pulses across all electrodes 204. For example, a voltage control system has been previously described in U.S. patent No. 6,240,117, published 2/29/2001, which is hereby incorporated by reference in its entirety.

The pressure control system 240 may be configured to control the fluorine concentration within the chamber 211 and provide a gas discharge medium 213 to the chamber 211. The pressure control system 240 may include a gas discharge line 242 and a vacuum line 244. The gas discharge line 242 may be configured to provide one or more gas components (e.g., He, Ne, Ar, Kr, Xe, F) of the gas discharge medium 213 to the chamber 211 ₂ 、Br ₂ 、CL ₂ Etc.). The vacuum line 244 may be configured to provide a negative pressure (e.g., draw) to a portion of the gas discharge medium 213 in the chamber 211, for example, during injection of one or more gas components into the gas discharge medium 213 through the gas discharge line 242. In some embodiments, the pressure control system 240 may include one or more gas sources (not shown), one or more pressure regulators (not shown), a vacuum pump (not shown), fluorine (F) ₂ ) A trap or other halogen trap, and/or a controller (not shown) for controlling the fluorine concentration in the chamber 211 and the refilling of the gas discharge medium 213 in the chamber 211. For example, a pressure control system has been previously described in U.S. patent No. 6,240,117, published 2/29 2001, which is hereby incorporated by reference in its entirety. In some embodiments, the pressure control system 240 may be coupled to the gas discharge stage 210 and configured to flow a portion of the gas discharge medium 213 with the metal fluoride dust 208 through the input port 214 of the MFT 300, through the MFT 300 (e.g., the packed bed filter assembly 400), and through the first output port 222 and/or the second output port 224 of the MFT 300.

Exemplary Metal Fluoride Traps (MFT)

Fig. 3 is a schematic cross-sectional view (taken along the plane indicated by III-III in fig. 2) of the MFT 300 of the light source apparatus 200 shown in fig. 2, according to an exemplary embodiment. Fig. 4 is a schematic cross-sectional view (taken along the plane indicated by IV-IV in fig. 3) of the packed bed filter assembly 400 of the MFT 300 shown in fig. 3, according to an exemplary embodiment.

In some embodiments, MFT 300 may be configured to trap metal fluoride dust 208 generated in gas discharge medium 213 in chamber 211 of gas discharge stage 210. MFT 300 may also be configured to reduce metal fluoride dust 208 accumulation on first optical window 218 and second optical window 220, and to improve the service life and laser performance of gas discharge stage 210 (e.g., MO). Although MFT 300 is illustrated in fig. 3 as a standalone device and/or system, embodiments of the present disclosure may also be used with other optical systems, such as, but not limited to, radiation source SO, lithographic device LA, light source device 200, and/or other optical systems. In some embodiments, the MFT 300 may be located outside the 3D frame 201 of the light source device 200. For example, the MFT 300 may be connected to the chamber 211 via the input port 214 and the first and

second output ports

222, 224, which extend such that the MFT 300 is located outside of the 3D frame 201.

In some embodiments, the MFT 300 may include an MFT frame 301, an input port 214 coupled to the chamber 211, a first output port 222 coupled to the chamber 211 and the first optical window 218, a second output port 224 coupled to the chamber 211 and the second optical window 220, an electrostatic precipitator 320, and a packed bed filter assembly 400. In some embodiments, MFT frame 301 may be cylindrical. For example, the MFT 301 framework may be about 10 millimeters (diameter) by about 100 millimeters (length).

In some embodiments, the input port 214 may be configured to pass a portion of the gas discharge medium 213 with metal fluoride dust 208 within the chamber 211 into the MFT 300. As shown in fig. 3, the gas discharge medium 213 may flow through the packed bed filter assembly 400 towards the electrostatic precipitator 320, and the metal fluoride dust 208 may be absorbed in the packed bed filter assembly 400. The first and

second output ports

222, 224 may be configured to pass portions of the gas discharge medium 213 (e.g., the cleaning gas from which the metal fluoride dust 208 is removed) that have passed through the packed bed filter assembly 400 and the electrostatic precipitator 320 in the MFT 300 back through the chamber 211 to the first and second

optical windows

218, 220, respectively.

In some embodiments, the electrostatic precipitator 320 may be configured to induce an electrical charge in the metal fluoride dust 208 flowing through the MFT 300 and promote adsorption of the remaining metal fluoride dust 208. The electrostatic precipitator 320 may include a center wire 322, a precipitation tube 324, and a high voltage source 328. A high voltage (e.g., several kV) may be applied to the center wire 322 via a high voltage source 328 to generate a strong electric field between the center wire 322 and an inner surface 326 of the dust removal tube 324 (e.g., grounded). In some embodiments, the center wire 322 may pass axially through a dust tube 324 (e.g., cylindrical) to create an electrostatic charge on the inner surface 326. When a high voltage difference (e.g., several kV) is applied between the center wire 322 and the inner surface 326, any residual metal fluoride dust 208 may adhere to the inner surface 326 after flowing through the packed bed filter assembly 400. The electrostatic precipitator 320 may extend beyond the first tube end mount 416 and the second tube end mount 418 of the packed bed filter assembly 400 along the length of the MFT 300.

In some embodiments, the packed bed filter assembly 400 may be configured to absorb the metal fluoride dust 208 flowing through the MFT 300. The packed bed filter assembly 400 may include packed

bed filters

402, 404 and a dust extraction tube assembly 410. The packed

bed filters

402, 404 may include

beads

406, 408 configured to absorb the metal fluoride dust 208. In some embodiments, as shown in fig. 3 and 4, packed

bed filters

402, 404 may be disposed around the electrostatic precipitator 320. In some embodiments, the total surface area (e.g., metal fluoride trapping capacity) of the packed

bed filters

402, 404 is defined by the

beads

406, 408. In some embodiments, the total surface area may be configured to control the flow of gas discharge medium 213 through MFT 300.

In some embodiments, the packed bed filter assembly 400 may include a plurality of packed

bed filters

402, 404 separated by baffles (e.g., second dust extraction pipe 414). For example, as shown in fig. 3 and 4, the packed bed filter assembly 400 may include a first (outer) packed bed filter 402 and a second (inner) packed bed filter 404 separated by a second dust removal pipe 414. In some embodiments, the packed bed filter assembly 400 may include different packed

bed filters

402, 404. For example, as shown in fig. 3 and 4, the packed bed filter assembly 400 may include a first (outer) packed bed filter 402 having a plurality of first beads 406 (e.g., large diameter, small surface area, low packing density, first material, first roughness, etc.), and a second (inner) packed bed filter 404, different from the first (outer) packed bed filter 402, having a plurality of second beads 408 (e.g., small diameter, large surface area, high packing density, second material, second roughness, etc.). For example, the first and second packed

bed filters

402, 404 may have

different beads

406, 408 of different diameters, different surface areas, different packing densities, and/or different materials. Furthermore, embodiments with three or more packed bed filters are also conceivable.

In some embodiments, the first packed bed filter 402 having the plurality of first beads 406 and the second packed bed filter 404 having the plurality of second beads 408 may be the same. For example, the plurality of first beads 406 and the plurality of second beads 408 may be identical (e.g., shape, size, material, etc.). In some embodiments, the first packed bed filter 402 having the plurality of first beads 406 and the second packed bed filter 404 having the plurality of second beads 408 may be different. For example, the plurality of first beads 406 and the plurality of second beads 408 can be different (e.g., shape, size, material, etc.).

In some embodiments, the first plurality of beads 406 and the second plurality of beads 408 can be arranged in the packed

bed filters

402, 404 as random loose fill (RLP), random close fill (RCP) (e.g., by shaking), single size spherical fill (e.g., Face Centered Cubic (FCC)), multi-size spherical fill (e.g., FCC with smaller diameter beads to fill the voids), and the like. For example, the plurality of first beads 406 and the plurality of second beads 408 may be arranged as RLP (e.g., packing density of about 60%), RCP (e.g., packing density of about 64%), single-size spherical packing (e.g., packing density of about 74%), and/or multi-size spherical packing (e.g., packing density of about 93%) in some embodiments, the first packed bed filter 402 and/or the second packed bed filter 404 may include both the plurality of first beads 406 and the plurality of second beads 408. For example, the plurality of first beads 406 and the plurality of second beads 408 may be arranged differently in the first packed bed filter 402 and the second packed bed filter 404 such that the first packed bed filter 402 has a different packing density and total surface area than the second packed bed filter 404.

In some embodiments, the

beads

406, 408 may be spherical. For example, the

beads

406, 408 may be about 1mm to about 10mm in diameter. In some embodiments, the diameter of the first plurality of beads 406 can be about 5mm to about 10mm, and the diameter of the second plurality of beads 408 can be about 1mm to about 5 mm. For example, the diameter of the first plurality of beads 406 may be about 5mm, and the diameter of the second plurality of beads 408 may be about 2 mm. In some embodiments, the

beads

406, 408 may have a smooth polished outer surface. For example, the

beads

406, 408 may be ball bearings. In some embodiments, the

beads

406, 408 may include fluoride corrosion resistant materials. For example, the

beads

406, 408 may include glass-like components, crystalline components, metals, and/or oxides. For example, the

beads

406, 408 may include aluminum, duralumin, alumina, nickel, monel, brass, copper, zinc, calcium boride, calcium fluoride, and/or some combination thereof. In some embodiments, the

beads

406, 408 may be of different materials. For example, the first plurality of beads 406 may include a first material (e.g., brass) and the second plurality of beads 408 may include a second material (e.g., alumina).

In some embodiments, the dust extraction tube assembly 410 may be configured to assemble the

beads

406, 408 in the packed bed filter assembly 400. The dusting tube assembly 410 may include dusting

tubes

412, 414, a first tube end mount 416 and a second tube end mount 418. The

dust extraction tubes

412, 414 may be disposed between a first tube end mount 416 and a second tube end mount 418. In some embodiments, the dust extraction tube assembly 410 may be cylindrical. For example, the

dust extraction tubes

412, 414 and the first and second tube end mounts 416, 418 may be cylindrical. In some embodiments, the dust extraction tube assembly 410 may include one or more baffles configured to direct the gas discharge media 213 to flow in the packed bed filter assembly 400 along the entire length of the packed bed filter assembly 400. For example, as shown in FIG. 3, the

dust tubes

412, 414 can include small openings 420, 422 (e.g., slots, notches, holes, etc.) at the distal ends of the

dust tubes

412, 414 to create a gap between the

dust tubes

412, 414 and the first 416 and second 418 tube end mounts.

In some embodiments, the dusting tube assembly 410 may include a plurality of dusting

tubes

412, 414 positioned between a first tube end holder 416 and a second tube end holder 418. For example, the dusting tube assembly 410 may include a first dusting tube 412 and a second dusting tube 414. In some embodiments, the first dust removal tube 412 and the second dust removal tube 414 may be concentric. For example, the first (outer) dust removal pipe 412 may be disposed with respect to the second (inner) dust removal pipe 414. In some embodiments, the dedusting tube assembly 410 can include a glass-like component, a crystalline component, a metal, and/or an oxide. For example, the

dust tubes

412, 414 may include aluminum, duralumin, alumina, nickel, monel, brass, copper, zinc, calcium boride, calcium fluoride, and/or some combination thereof.

Exemplary flow chart

Fig. 5 illustrates a flow diagram 500 for trapping metal fluoride dust 208 in a gas discharge stage 210 according to one embodiment. It should be understood that not all of the steps in fig. 5 are required to perform the disclosure provided herein. Further, some steps may be performed simultaneously, sequentially, and/or in a different order than shown in fig. 5. Flowchart 500 will be described below with reference to fig. 2 through 4. However, flowchart 500 is not limited to these example embodiments.

In step 502, as shown in the example of fig. 3 and 4, a dust extraction tube assembly 410 may be assembled, the dust extraction tube assembly 410 including a first dust extraction tube 412 and a second dust extraction tube 414 positioned between a first tube end support 416 and a second tube end support 418. In some embodiments, the first dust removal tube 412 and the second dust removal tube 414 may be concentrically arranged in the dust removal tube assembly 410. For example, the first (outer) dust removal pipe 412 may be disposed with respect to the second (inner) dust removal pipe 414. In some embodiments, the dusting tube assembly 410 may comprise one or more baffles for spacing the plurality of first beads 406 and the plurality of second beads 408. For example, the second dust extraction duct 414 may have a shortened length to form openings (e.g., a first small opening 420 and a second small opening 422) and act as baffles disposed between the plurality of first beads 406 and the plurality of second beads 408.

In step 504, as shown in the example of fig. 3 and 4, the plurality of packed

bed filters

402, 404 in the dust extraction tube assembly 410 may be assembled around the electrostatic precipitator 320 to form the packed bed filter assembly 400. Each packed

bed filter

402, 404 comprises a plurality of

beads

406, 408 configured to absorb the metal fluoride dust 208 in the gas discharge medium 213. In some embodiments, assembling the plurality of packed

bed filters

402, 404 includes packing the plurality of

beads

406, 408 between the plurality of

dust extraction tubes

412, 414. For example, the plurality of first beads 406 may be filled between the first dust removal duct 412 and the second dust removal duct 414, and the plurality of second beads 408 may be filled between the second dust removal duct 414 and the electrostatic precipitator 320. In some embodiments, the packing includes packing a plurality of first beads 406 between first dust removal tube 412 and second dust removal tube 414, the plurality of first beads 406 being different from packing a plurality of second beads 408 between second dust removal tube 414 and electrostatic precipitator 320. For example, the plurality of first beads 406 can have a different diameter, surface area, bulk density, material, and/or combination of beads than the plurality of second beads 408.

In step 506, as shown in the example of fig. 3 and 4, the packed bed filter assembly 400 may be inserted into the MFT 300.

In step 508, as shown in the examples of fig. 2-4, gas-discharge medium 213 may be directed to flow through MFT 300.

In step 510, as shown in the examples of fig. 2-4, the metal fluoride dust 208 may be tapered in the packed bed filter assembly 400.

In some embodiments, the method may further include removing the plurality of

beads

406, 408 from the packed bed filter assembly 400, washing the plurality of

beads

406, 408, and reassembling the plurality of

beads

406, 408 in the packed bed filter assembly 400. In some embodiments, the method may further include removing the plurality of

beads

406, 408 from the packed bed filter assembly 400, and reassembling a second plurality of beads (e.g., new beads similar to beads 406, 408) in the packed bed filter assembly 400.

Although specific reference may be made in this text to the use of lithographic apparatus in the manufacture of ICs, it should be understood that the lithographic apparatus described herein may have other applications, such as the manufacture of integrated optical systems, the manufacture of guidance and detection patterns for magnetic domain memories, the manufacture of flat-panel displays, the manufacture of LCDs, the manufacture of thin-film magnetic heads, etc. Those skilled in the art will appreciate that, in the context of such alternative applications, any use of the terms "wafer" or "mold" herein should be considered as synonymous with the more general terms "substrate" or "target portion", respectively. The substrate referred to herein may be processed, before or after exposure, in for example a track unit (a tool that typically applies a layer of resist to a substrate and develops the exposed resist), a metrology unit and/or an inspection unit. Where applicable, the disclosure herein may be applied to these and other substrate processing tools. Further, the substrate may be processed more than once, for example in order to create a multi-layer IC, so that the term substrate used herein may also refer to a substrate that already contains multiple processed layers.

Although specific reference may have been made above to the use of embodiments in the context of optical lithography, it will be appreciated that embodiments may also be used in other applications, for example imprint lithography, and where the context allows, are not limited to optical lithography. In imprint lithography, the topography of a patterning device defines the pattern formed on a substrate. When the resist is cured by applying electromagnetic radiation, heat, pressure, or a combination thereof, the topography of the patterning device may be pressed into a resist layer provided to the substrate. After the resist is cured, the patterning device is moved out of the resist, leaving a pattern in the resist.

It is to be understood that the phraseology or terminology herein is for the purpose of description and not of limitation, such that the terminology or phraseology of the present specification is to be interpreted by the skilled artisan in light of the teachings herein.

As used herein, the term "substrate" describes a material on which a layer of material is added. In some embodiments, the substrate itself may be patterned, and the material added on top of the substrate may also be patterned, or may remain unpatterned.

The following examples are illustrative, but non-limiting, examples of the embodiments of the present disclosure. Other suitable modifications and adaptations of various conditions and parameters normally encountered in the art and which would be apparent to those skilled in the relevant art(s) fall within the spirit and scope of the present disclosure.

Although specific reference may be made in this text to the use of the above-described apparatus and/or system in the manufacture of ICs, it should be clearly understood that there are many other possible applications for such apparatus and/or system. For example, it can be applied to integrated optical system fabrication, guidance and detection pattern fabrication of magnetic domain memories, LCD panel fabrication, thin film magnetic head fabrication, and the like. Those skilled in the art will understand that in the context of such alternative applications, any use of the terms "reticle", "wafer" or "mold" herein should be considered as being replaced by the more general terms "mask", "substrate" and "target portion", respectively.

Although specific embodiments have been described above, it will be appreciated that these embodiments may be practiced otherwise than as described. This description is not intended to limit the scope of the claims.

It should be understood that the detailed description section, and not the summary and abstract sections, is intended to be used to interpret the claims. The summary and abstract sections may set forth one or more, but not all exemplary embodiments contemplated by the inventor(s), and are therefore not intended to limit the embodiments and the appended claims in any way.

Embodiments have been described above with the aid of functional building blocks illustrating the implementation of specific functions and relationships thereof. Boundaries of these functional building blocks have been arbitrarily defined herein for the convenience of the description. Alternate boundaries may be defined so long as the specified functions and relationships thereof are appropriately performed.

The foregoing description of the specific embodiments will so fully reveal the general nature of the embodiments that others can, by applying knowledge within the skill of the art, readily modify and/or adapt for various applications such specific embodiments without undue experimentation, without departing from the general concept of the embodiments. Therefore, such adaptations and modifications are intended to be within the meaning and range of equivalents of the disclosed embodiments, based on the teaching and guidance presented herein.

Other aspects of the invention are set forth in the following numbered clauses.

1. A light source device comprising: a gas discharge stage comprising: an optical amplifier comprising a chamber configured to hold a gas discharge medium that outputs a beam of light; and an optical element, the set of optical elements configured to form an optical resonator around the optical amplifier; and a metal fluoride trap configured to trap metal fluoride dust generated from the gas discharge stage, the metal fluoride trap comprising: an electrostatic precipitator; and a packed bed filter disposed around the electrostatic precipitator, wherein the packed bed filter comprises a plurality of beads configured to absorb metal fluoride dust.

2. The light source apparatus of clause 1, wherein the packed bed filter comprises a total surface area configured to control a flow rate of the gas discharge medium through the metal fluoride trap.

3. The light source apparatus of clause 1, wherein the packed bed filter comprises a plurality of packed bed filters separated by baffles.

4. The light source apparatus according to clause 3, wherein the plurality of packed bed filters are different from each other.

5. The light source apparatus according to clause 4, wherein the plurality of packed bed filters differ in surface area.

6. The light source device according to clause 4, wherein the plurality of packed bed filters are different in packing density.

7. The light source apparatus of clause 1, wherein the plurality of beads are spherical and include a smooth polished outer surface.

8. The light source apparatus of clause 1, wherein the plurality of beads comprises a fluoride corrosion resistant material.

9. The light source device according to clause 1, wherein the plurality of beads includes a plurality of first beads, and a plurality of second beads different from the plurality of first beads.

10. The light source device of clause 1, wherein the gas discharge medium comprises an excimer medium.

11. The light source device according to clause 10, wherein the gas discharge medium includes F ₂ ArF, KrF and/or XeF.

12. The light source apparatus of clause 1, wherein the set of optical elements comprises: an Optical Coupler (OC) in optical communication with the first optical port of the chamber; and a line width narrowing module (LNM) in optical communication with the second optical port of the chamber.

13. The light source device according to clause 1, further comprising: a pressure control system coupled to the gas discharge stage and configured to direct a portion of the gas discharge medium to flow through the input port of the metal fluoride trap, through the packed bed filter, and through one or more output ports of the metal fluoride trap.

14. A metal fluoride trap configured to trap metal fluoride dust generated in a gas discharge medium of a gas discharge stage, the metal fluoride trap comprising: an electrostatic precipitator; and a packed bed filter disposed around the electrostatic precipitator, wherein the packed bed filter comprises a plurality of beads configured to absorb metal fluoride dust in the gas discharge medium.

15. The metal fluoride trap of clause 14, wherein the packed bed filter comprises a total surface area configured to control a flow of the gas discharge medium through the metal fluoride trap.

16. The metal fluoride trap of clause 14, wherein the plurality of beads are all spherical.

17. The metal fluoride trap of clause 16, wherein each bead has a diameter of about 1mm to about 10 mm.

18. The metal fluoride trap of clause 16, wherein each bead comprises a smooth polished outer surface.

19. The metal fluoride trap of clause 14, wherein the plurality of beads comprises a fluoride corrosion resistant material.

20. The metal fluoride trap of clause 19, wherein the fluoride corrosion resistant material comprises a glass-like component, a crystalline component, a metal, and/or an oxide.

21. The metal fluoride trap of clause 19, wherein the fluoride corrosion resistant material comprises aluminum, duralumin, alumina, nickel, monel, brass, copper, zinc, calcium boride, and/or calcium fluoride.

22. The metal fluoride trap of clause 14, wherein the plurality of beads comprises a first plurality of beads and a second plurality of beads different from the first plurality of beads.

23. The metal fluoride trap of clause 22, wherein the first plurality of beads has a first size and the second plurality of beads has a second size different from the first size.

24. The metal fluoride trap of clause 22, wherein the plurality of first beads comprises a first material and the plurality of second beads comprises a second material different from the first material.

25. A method of trapping metal fluoride dust generated in a gas discharge medium of a gas discharge stage within a metal fluoride trap, said method comprising: assembling a dust extraction tube assembly comprising a plurality of dust extraction tubes located between a first tube end support and a second tube end support; surrounding an electrostatic precipitator, a plurality of packed bed filters assembled in the dedusting tube assembly to form a packed bed filter assembly, wherein each packed bed filter comprises a plurality of beads configured to absorb metal fluoride dust in the gas discharge media; inserting the packed bed filter assembly into the metal fluoride trap; directing the gas discharge medium through the metal fluoride trap; and trapping metal fluoride dust in the packed bed filter assembly.

26. The method of clause 25, wherein assembling the plurality of packed bed filters comprises filling the plurality of beads between the plurality of dust extraction tubes.

27. The method of clause 26, wherein the filling comprises filling a plurality of inner beads in a plurality of inner dust extraction tubes, and filling a plurality of outer beads different from the plurality of inner beads in a plurality of outer dust extraction tubes.

28. The method of clause 27, wherein the plurality of outer beads have a different surface area and/or packing density than the plurality of inner beads.

29. The method of clause 25, further comprising: removing the plurality of beads from the packed bed filter assembly, washing the plurality of beads, and reassembling the plurality of beads in the packed bed filter assembly.

30. The method of clause 25, further comprising removing the plurality of beads from the packed bed filter assembly and reassembling a second plurality of beads in the packed bed filter assembly.

The breadth and scope of an embodiment should not be limited by any of the above-described exemplary embodiments, but should be defined only in accordance with the following claims and their equivalents.

Claims

1. A light source device comprising:

a gas discharge stage comprising:

an optical amplifier comprising a chamber configured to hold a gas discharge medium that outputs a beam of light; and

a set of optical elements configured to form an optical resonator around the optical amplifier; and

a metal fluoride trap configured to trap metal fluoride dust generated from the gas discharge stage, the metal fluoride trap comprising:

an electrostatic precipitator; and

a packed bed filter disposed around the electrostatic precipitator,

wherein the packed bed filter comprises a plurality of beads configured to absorb metal fluoride dust.

2. The light source apparatus of claim 1, wherein the packed bed filter comprises a total surface area configured to control a flow of the gas discharge medium through the metal fluoride trap.

3. The light source apparatus of claim 1, wherein the packed bed filter comprises a plurality of packed bed filters separated by baffles.

4. The light source apparatus of claim 3, wherein the plurality of packed bed filters are different from one another.

5. The light source apparatus of claim 4, wherein the plurality of packed bed filters differ in surface area.

6. The light source device according to claim 4, wherein the plurality of packed bed filters are different in packing density.

7. The light source apparatus of claim 1, wherein the plurality of beads are each spherical and comprise a smooth polished outer surface.

8. The light source apparatus of claim 1, wherein the plurality of beads comprises a fluoride corrosion resistant material.

9. The light source device according to claim 1, wherein the plurality of beads includes a plurality of first beads and a plurality of second beads different from the plurality of first beads.

10. The light source device of claim 1, wherein the gas discharge medium comprises an excimer medium.

11. The light source device of claim 10, wherein the gas discharge medium comprises F ₂ ArF, KrF and/or XeF.

12. The light source device of claim 1, wherein the set of optical elements comprises:

an Optical Coupler (OC) in optical communication with the first optical port of the chamber; and

a line width narrowing module (LNM) in optical communication with the second optical port of the chamber.

13. The light source device of claim 1, further comprising:

a pressure control system coupled to the gas discharge stage and configured to direct a portion of the gas discharge medium to flow through the input port of the metal fluoride trap, through the packed bed filter, and through one or more output ports of the metal fluoride trap.

14. A metal fluoride trap configured to trap metal fluoride dust generated in a gas discharge medium of a gas discharge stage, the metal fluoride trap comprising:

an electrostatic precipitator; and

a packed bed filter disposed around the electrostatic precipitator,

wherein the packed bed filter comprises a plurality of beads configured to absorb metal fluoride dust in the gas discharge medium.

15. The metal fluoride trap of claim 14, wherein the packed bed filter comprises a total surface area configured to control flow of the gas discharge medium through the metal fluoride trap.

16. The metal fluoride trap of claim 14, wherein the plurality of beads are all spherical.

17. The metal fluoride trap of claim 16, wherein each bead is about 1mm to about 10mm in diameter.

18. The metal fluoride trap of claim 16, wherein each bead includes a smooth polished outer surface.

19. The metal fluoride trap of claim 14, wherein the plurality of beads comprises a fluoride corrosion resistant material.

20. The metal fluoride trap of claim 19, wherein the fluoride corrosion resistant material comprises a glass-like component, a crystalline component, a metal, and/or an oxide.

21. The metal fluoride trap of claim 19, wherein the fluoride corrosion resistant material comprises aluminum, duralumin, alumina, nickel, monel, brass, copper, zinc, calcium boride, and/or calcium fluoride.

22. The metal fluoride trap of claim 14, wherein the plurality of beads comprises a first plurality of beads and a second plurality of beads different from the first plurality of beads.

23. The metal fluoride trap of claim 22, wherein the first plurality of beads have a first size and the second plurality of beads have a second size different from the first size.

24. The metal fluoride trap of claim 22, wherein the first plurality of beads comprises a first material and the second plurality of beads comprises a second material different from the first material.

25. A method of trapping metal fluoride dust generated in a gas discharge medium of a gas discharge stage in a metal fluoride trap, the method comprising:

assembling a dust extraction tube assembly comprising a plurality of dust extraction tubes located between a first tube end support and a second tube end support;

assembling a plurality of packed bed filters in the dedusting tube assembly around an electrostatic precipitator to form a packed bed filter assembly, wherein each packed bed filter comprises a plurality of beads configured to absorb metal fluoride dust in the gas discharge media;

inserting the packed bed filter assembly into the metal fluoride trap;

directing the gas discharge medium through the metal fluoride trap; and

trapping metal fluoride dust in the packed bed filter assembly.

26. The method of claim 25, wherein assembling the plurality of packed bed filters comprises packing the plurality of beads between the plurality of dust extraction tubes.

27. The method of claim 26, wherein said filling comprises filling a plurality of inner beads in a plurality of inner dust extraction tubes, and filling a plurality of outer beads different from said plurality of inner beads in a plurality of outer dust extraction tubes.

28. The method of claim 27, wherein the plurality of outer beads have a different surface area and/or packing density than the plurality of inner beads.

29. The method of claim 25, further comprising: removing the plurality of beads from the packed bed filter assembly, washing the plurality of beads, and reassembling the plurality of beads in the packed bed filter assembly.

30. A method according to claim 25, further comprising removing the plurality of beads from the packed bed filter assembly and reassembling a second plurality of beads in the packed bed filter assembly.